JPS5832480Y2 - Speed control circuit for visual motor with voltage compensation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant speed control circuit for a DC motor in, for example, a tape recorder, a video tape recorder, etc., and more particularly to a speed control circuit for a DC motor with voltage compensation.

Generally, when controlling a DC motor used in the above-mentioned devices at a constant speed, if the power supply voltage supplied to the constant speed control circuit fluctuates, the control state changes as the reference voltage fluctuates, causing the motor's rotational speed to change. deviates from the required constant speed rotation.

For this reason, in conventional motors that control the motor at a constant speed, a constant voltage circuit is provided between the control circuit and the power source so that the voltage supplied to the control circuit is constant.

However, providing the above-mentioned constant voltage circuit not only increases the number of components in the circuit configuration, but also has disadvantages such as higher economic costs and a limited range of voltage usage as a constant voltage circuit. Was.

The present invention eliminates the above-mentioned drawbacks of the conventional technology, and eliminates the need to provide a constant voltage circuit between the above-mentioned control circuit and the power supply voltage, and eliminates fluctuations in the rotational speed of the motor due to fluctuations in the power supply voltage. It is an object of the present invention to provide a speed control circuit for a DC motor having voltage compensation that can prevent the above voltage fluctuations and compensate for the above voltage fluctuations with a simple circuit configuration.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a motor speed control circuit according to the present invention. Briefly, 1 is a power supply voltage supply terminal to which a power supply voltage (2) is supplied.

The power supply voltage A from the end terminal 1 is applied to a voltage dividing circuit consisting of series-connected diodes D1 and D2, resistors RB and AA, and a reference voltage V is applied from the connection point of the voltage dividing resistors RB and RA.
It is added to comparator 2 as r.

On the other hand, the rotation from the motor M is applied to a frequency generator FG as a rotation speed detection means and is taken out as an alternating current signal.

The alternating current signal from the frequency generator FG is extracted as a rectangular wave by an amplifier 3 having an amplitude limiting function, and then a differential pulse corresponding to the frequency of the alternating current signal is formed by a differential pulse generator 4, and a differential pulse corresponding to the frequency of the alternating current signal is formed by a frequency-voltage converter. (hereinafter abbreviated as an F-V converter) 5 extracts a voltage corresponding to the frequency of the differential pulse as a sawtooth voltage.

The above-mentioned sawtooth wave converted into a voltage by the above-mentioned F-V converter 5 is applied to the above-mentioned comparator 2 as the comparison signal voltage vs, where it is compared with the above-mentioned reference voltage Vr, and the comparison error voltage is used as the control signal voltage Vr. The current is applied to the motor M via the low-pass filter 6 and the DC amplifier 7, and the rotational speed of the motor M is controlled.

Therefore, the comparison signal voltage Vs, which is the output of the F-V converter 5, is affected by fluctuations in the power supply voltage V.
The amount of change Δvs is as follows.

That is, (VS+Δvs)/Vs=(V+ΔV)/V(
V: power supply voltage, vS: comparison signal voltage, Vr two reference voltage)
Therefore, .

Next, in a steady state, the deviation becomes zero (that is, the output of the comparator 2 becomes zero).

), then Vs=Vr.

If Vs=vr, naturally Δvr=ΔVs, and even if the power supply voltage V fluctuates by ΔV, the rotational speed of the motor remains constant.

That is, as is well known, the voltage supplied to the motor is not determined by the power supply voltage V, but in the present invention.

Since it is determined by a servo circuit such as a motor speed control circuit, fluctuations in the power supply voltage V have no effect on the motor rotation speed.

Therefore, the amount of change ΔVr in the reference voltage Vr should be as follows.

On the other hand, the reference voltage Vr at the connection point of the voltage dividing resistors RB and RA in FIG. D2 forward voltage V
F, the forward junction voltage between the base and emitter of the transistor constituting the comparator 2 that compares the reference voltage Vr and the comparison signal voltage VS (corresponding to the forward junction voltage between the base and the eminter), then Vr=(V-2VF)·α+VBE (3).

Note that α in the above equation (3) indicates the voltage division ratio determined by the resistors RB and RA.

Furthermore, when the fluctuations of Vr and ■ in equation (3) are taken into account, equation (4) is obtained.

V, +liV, = (V+=iV-2VF) ・a+VB
E (4) Therefore, by substituting vr in equation (3) into equation (4), △Vr2△V·α is obtained.

Also, from equations (2), (3), and (5) above, V・a
=Vr=(V-2VF) °α+VBE Here, a commonly used diode (DI
, D2), and the forward junction voltage VBE between the base and eminter of the transistor is almost equal, so if VBE - VF, equation (7) becomes ■ α - (8), and the above By selecting the partial pressure ratio α as shown in equation (8), △vr=△Vs holds true.

That is, in the present invention, two diodes are used and the above-mentioned voltage division ratio α is selected.

Note that if no diode is used, the above α will be infinite, and if one diode is used, α will be
becomes l, and both of these are impractical.

If three or more diodes are used, each is 1. α=□1. α = □..., so it is not practical. However, in the embodiment of this invention, α knee is the optimal control condition, and since a reference voltage suitable for control can be obtained, the diode used is The number is □ as 2.

In addition, in the above equation (8), α knee was explained, but in reality, VBEL:=VF, so equation (8) is α
It becomes common.

FIG. 2 is an actual circuit diagram of the block diagram shown in FIG. 1.

Note that the areas indicated by (2) to (7) in the figure correspond to the comparators 2 and 3 described in the block diagram of FIG. 3. Amplifier with amplitude limiting action; 4. Differential pulser; F-V converter5. A low-pass filter 6 and a DC amplifier r are each shown.

Next, the operation of this circuit will be explained. The power supply voltage V from the power supply voltage supply terminal 1 is applied to the connection point between the resistors R4 and R5 by a voltage dividing circuit consisting of diodes DI and D2 connected between the ground and resistors R3, R4, and R5. It is given as a reference voltage vr with a required voltage division ratio.

Note that the resistor R5 is the same as the resistor RA in FIG. 1, and the resistor R3,
R4, (Th) corresponds to the resistor RB in Fig. 1, and the resistor R4
Th, which is connected in parallel to
It's a star.

Thus, the reference voltage ■1 is applied to the point A of the transistor Q3 constituting the comparator 2 as described above.

Then, the rotation of the motor M is taken out as an AC signal corresponding to the rotation of the motor M from a frequency generator FG serving as a rotation speed detection means, and is applied to the base of the transistor Q1. When the waveform is shaped into a rectangular wave pulse by the width filter 3, the width of ζ is also amplified.

The rectangular wave pulse that is the output of this transistor Q1 is connected to a capacitor C1 provided on the output side of the transistor Q1.
It is differentiated by a differential pulse generator 4 made up of a resistor R1 and applied to the base of a transistor Q2.

The period of the differentiated pulse above is determined by the frequency generator F
Needless to say, it is equal to the period of the alternating current signal that is the output of the motor M, and changes in accordance with the above-mentioned signal (that is, the number of rotations of the motor M).

The above-mentioned transistor Q2 constitutes the F-V converter 5, to which the above-mentioned differential pulse is input, and on the output side, a sawtooth voltage as a comparison signal is obtained across the capacitor C2 by charging and discharging it.

Incidentally, the variable resistor VR inserted in series with the resistor R2 on the collector side of the transistor Q2 is connected to the above-mentioned capacitor C.
This is to adjust the charging time constant of No. 2, and to set the slope of the sawtooth wave during the charging period.

A sawtooth voltage converted to a voltage as a comparison signal is obtained at the output of the transistor Q2 of the F-V converter 5, and this signal is added to the E33 point of the transistor Q3 of the comparator 2 as the comparison signal voltage Vs. It will be done.

In the transistor Q3, both the reference voltage vr applied to the vine and the comparison signal voltage VS applied to the base are compared, and when the first value of the comparison signal voltage Vs exceeds the reference voltage Vr, the A pulse-like signal corresponding to the portion is taken out at the output.

The pulsed signal taken out from here is smoothed by a low-pass filter 6 consisting of a resistor R6 and a capacitor C3 to become a DC voltage, and then further transistors Q4 and Q
The voltage is amplified by a DC amplifier 7 consisting of a DC amplifier 7, which controls the drive of the motor Mft.

That is, the output of the transistor Q3 is smoothed by the low-pass filter 6 to form a DC voltage, and depending on the level of the DC voltage, the output of the transistor Q4. Q5 is driven and controlled.

Therefore, when the level difference between the comparison signal voltage Vs and the reference voltage Vr is large, the output of the transistor Q3, that is, the level of the above-mentioned DC voltage that drives the transistors Q4 and Q5 also becomes a dog, and the motor M follows this and drives the motor M. This is a control operation when the rotational speed of the motor M is slower than normal.

In this case, it means that the period of the differential pulse described above, that is, the period of the sawtooth voltage waveform as the comparison signal is long.

Furthermore, when the rotational speed of the motor M is faster than normal, the level difference between the comparison signal voltage Vs and the reference voltage ■1 becomes small, and the output of the transistor Q3, that is, the above DC voltage that drives the transistors Q4 and Q5. The level of the motor M decreases, and the rotational speed of the motor M is controlled to be slow.

In this case, it means that the period of the sawtooth voltage as a comparison signal is shorter than in normal times.

That is, when the rotational speed of the motor M is faster or slower than normal, the frequency of the AC signal output from the frequency generator FG becomes higher or lower, and the comparison signal follows this. The leading voltage of the sawtooth wave voltage becomes lower or higher, respectively, and a control drive signal as a DC voltage is obtained according to the level difference with the reference voltage .
The rotation speed of is controlled.

As described above, according to the present invention, two diodes are inserted in the voltage dividing circuit that obtains the reference voltage, and the voltage dividing ratio α is selected as αζ−. A DC motor with voltage compensation that allows the motor to rotate at a constant speed even when the signal voltage fluctuates, and also provides a wide voltage usage range that is not limited by the power supply voltage without using a constant voltage circuit that increases costs. speed control circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a speed control circuit showing one embodiment of the present invention, and FIG. 2 is an electric circuit diagram showing one embodiment thereof. 1... Power supply voltage supply terminal, Dl, D2...
・・・Diode, RA, RB・・・・・・Voltage dividing resistor, 2
... Comparator, 3 ... Amplitude limiter and amplifier, 4 ... Differential pulse generator, 5 ... F-■
Converter, 6...Low pass filter, 1...
...DC amplifier, M...DC motor, FG...
...Frequency generator, Vr...Reference voltage, V
s...Comparison signal voltage.

Claims (1)

[Claims for Utility Model Registration] A reference voltage obtained by dividing the power supply voltage from a power supply terminal using a voltage dividing circuit, and a frequency generator detecting the rotational speed of a DC motor to obtain an AC signal. The AC signal is further converted into voltage by a frequency-voltage converter, and this signal is used as a comparison signal voltage to compare with the reference voltage to control the speed of the DC motor. A direct current motor equipped with voltage compensation, characterized in that it is constituted by a series circuit of diodes D1...Dn (n is an integer of 2 or more) and voltage dividing resistors RA and RB, and the voltage dividing ratio α is selected to be Speed control circuit.